This research project is designed to characterize the components of the normal human lung surfactant system and to evaluate the mechanisms, extent and significance of surfactant alterations which may accompany the progression of diffuse alveolar damage in patients treated for adult respiratory distress syndrome (ARDS). The results obtained during the past year clearly demonstrated that surgically excised lung specimens, postmortem lung specimens and tracheal aspirates are suitable sources for the isolation of human surfactant. We have already characterized the phospholipid composition of normal adult human surfactant and made considerable progress in the isolation and characterization of lung specific proteins. These proteins are somewhat different than those found in other animal species, although the major peptide subunits appear to be common in most animal species studied. In addition, we have begun to evaluate the phospholipid composition of surfactant isolated from tracheal aspirates of patients with ARDS. The preliminary data are promising with respect to our search for biochemical markers of lung surfactant damage. Our major research goal for the coming year is to correlate surfactant changes found in serial tracheal aspirates and postmortem lung tissues from patients with ARDS with clinical pathological data. We will also continue our studies of normal lung human surfactant with emphasis on the quantitation of minor lipid components and lung specific proteins.